You can send any data via AMF. In the case of uploading a
file though, Flex does not let the developer control what happens
after the user hits open in browse dialog. It will make a normal
multitype/form-data POST request. The new Flash player 10 when it
be able to do this.
But in AIR, you can read the contents of the file into a
ByteArray and send that across via remoteobject.